This invention relates to a system for monitoring and delivering medication to a patient. More specifically, the present invention is directed toward a device that monitors the risk to a patient of an automated therapy decision and allows a clinician to customize rules that determine whether an automated change in therapy is to be allowed or whether user/clinician intervention should be required based upon the risk of automation and the customized rules.
Diabetes is a metabolic disorder that afflicts tens of millions of people throughout the world. Diabetes results from the inability of the body to properly utilize and metabolize carbohydrates, particularly glucose. Normally, the finely tuned balance between glucose in the blood and glucose in bodily tissue cells is maintained by insulin, a hormone produced by the pancreas which controls, among other things, the transfer of glucose from blood into body tissue cells. Upsetting this balance causes many complications and pathologies including heart disease, coronary and peripheral artery sclerosis, peripheral neuropathies, retinal damage, cataracts, hypertension, coma, and death from hypoglycemic shock.
In patients with insulin-dependent diabetes the symptoms of the disease can be controlled by administering additional insulin (or other agents that have similar effects) by injection or by external or implantable insulin pumps. The correct insulin dosage is a function of the level of glucose in the blood. Ideally, insulin administration should be continuously readjusted in response to changes in blood glucose level. In diabetes management, insulin enables the uptake of glucose by the body's cells from the blood. Glucagon acts opposite to insulin and causes the liver to release glucose into the blood stream. The basal rate is the rate of continuous supply of insulin provided by an insulin delivery device (pump). The bolus is the specific amount of insulin that is given to raise blood concentration of the insulin to an effective level when needed (as opposed to continuous).
Presently, systems are available for continuously monitoring blood glucose levels by inserting a glucose sensitive probe into the patient's subcutaneous layer or vascular compartment or, alternately, by periodically drawing blood from a vascular access point to a sensor. Such probes measure various properties of blood or other tissues including optical absorption, electrochemical potential, and enzymatic products. The output of such sensors can be communicated to a hand held device that is used to calculate an appropriate dosage of insulin to be delivered into the blood stream in view of several factors such as a patient's present glucose level and rate of change, insulin administration rate, carbohydrates consumed or to be consumed, steroid usage, renal and hepatic status and exercise. These calculations can then be used to control a pump that delivers the insulin either at a controlled basal rate or as a periodic or one-time bolus. When provided as an integrated system the continuous glucose monitor, controller, and pump work together to provide continuous glucose monitoring and insulin pump control.
Such systems at present require intervention by a patient or clinician to calculate and control the amount of insulin to be delivered. However, there may be periods when the patient is not able to adjust insulin delivery. For example, when the patient is sleeping he or she cannot intervene in the delivery of insulin yet control of a patient's glucose level is still necessary. A system capable of integrating and automating the functions of glucose monitoring and controlled insulin delivery would be useful in assisting patients in maintaining their glucose levels, especially during periods of the day when they are unable to intervene.
Alternately, in the hospital environment an optimal glucose management system involves frequent adjustments to insulin delivery rates in response to the variables previously mentioned. However, constant intervention on the part of the clinician is burdensome and most glucose management systems are designed to maximize the time interval between insulin updates. A system capable of safely automating low-risk decisions for insulin delivery would be useful in improving patient insulin therapy and supporting clinician workflow.
Since the year 2000 at least five continuous or semi-continuous glucose monitors have received regulatory approval. In combination with continuous subcutaneous insulin infusion (CSII), these devices have promoted research toward closed loop systems which deliver insulin according to real time needs as opposed to open loop systems which lack the real time responsiveness to changing glucose levels. A closed loop system, also called the artificial pancreas, consists of three components: a glucose monitoring device such as a continuous glucose monitor (CGM) that measures subcutaneous glucose concentration (SC); a titrating algorithm to compute the amount of analyte such as insulin and/or glucagon to be delivered; and one or more analyte pumps to deliver computed analyte doses subcutaneously. Several prototype systems have been developed, tested, and reported based on evaluation in clinical and simulated home settings. This concerted effort promises accelerated progress toward home testing of closed loop systems.
Similarly, closed loop systems have been proposed for the hospital setting and investigational devices have been developed and tested, primarily through animal studies. In addition, several manufacturers are either in the process of developing or have submitted to the FDA automated glucose measurement systems designed for inpatient testing. Such systems will accelerate the development of fully automated systems for inpatient glucose management.
The primary problem with closed loop control or full automation of insulin therapy is that a computerized system makes decisions that may be high risk in terms of potential consequences if the patient's condition changes or differs from the assumptions behind the computerized decision system. As a result of the automation these high risk decisions are not uncovered until the risk is realized and the patient displays an unacceptable medical condition. Second, in the event of a device failure or medication management system or MMS failure, action is required by the automated system despite the potential lack of information. Third, in scenarios in which frequent glucose measurements are automatically collected but automation is not desired, it is undesirable to update the infusion at the same frequency as glucose measurements are collected. Fourth, when user intervention is required it may be undesirable or difficult for a clinician to respond at the bedside. For example, if the patient is in an isolation room but is observable the clinician may desire to update the infusion rate without entering the room.
Thus, a principle object of the invention is to provide an improved system for monitoring and delivering medication to a patient that makes risk determinations before providing therapy.
Another object of the invention is to provide a system that minimizes patient risk by mapping device failure, patient state and condition, and uncertainty.
Yet another object of the invention is to provide a system for monitoring and delivering medication to a patient that minimizes the risk to a patient.
Another object of the invention is to provide a system for monitoring and delivering medication that is able to selectively request for a user intervention.
These and other objects, features, or advantages of the invention will become apparent from the specification and claims.